This invention relates to a compressive molding machine for powder material in order to mold tablets for medical purpose or the like by compressing powder material.
Conventionally, in a compressive molding machine for powder material to fill powder material into a die and to compressively mold the powder material by the use of an upper punch and a lower punch inserted into the die, the powder material might splash and the splashed powder material might attach to the upper punch or the inside of an upper punch holding bore that holds the upper punch during, for example, a process of scraping the powder material after the powder material is filled into the die, or a process of compressively molding the powder material in the die with the upper punch and the lower punch. If the powder material attaches to the upper punch, a problem might occur that the attached powder material is mixed with lubricant applied to the upper punch, the mixture of the powder material and the lubricant becomes a lump and drops, and the mixture mixes into the powder material to be molded. In addition, if the powder material attaches to the inside of the upper punch holding bore, a problem might occur that the powder material is mixed with lubricant applied to the inside of the upper punch holding bore, the mixture of the powder material and the lubricant becomes a lump and drops and the mixture mixes into the powder material to be molded, or a problem might occur that the lumped mixture gets stuck inside the upper punch holding bore, which requires a troublesome labor of cleaning the inside of the upper punch holding bore. In order to prevent these problems, an arrangement is conceived that an upper punch dust-proof unit having an expandably elastic bellows part that surrounds a sliding part of the upper punch and whose upper end makes an abutting contact with the rotary turret is mounted. In the upper punch dust-proof unit having the bellows part, an arrangement of making the inside of the bellows part communicate with the outside of the bellows part is conceived that an air vent groove that is communicated with the upper punch holding bore and that extends along the upper punch holding bore is arranged in order to make it possible to interchange air between the inside of the bellows part and the outside thereof at a time that the bellows part is compressed to be shortened or extended. (For example, refer to a patent document 1) Patent document 1: Japanese Utility Model Publication No. SHO55-41439
At a time when the bellows part fails to extend with following a downward movement of the upper punch and the powder material might enter inside of the upper punch holding bore from a gap formed above the bellows part through the air vent groove. At this time, in case that an air vent groove that is communicated with the upper punch holding bore and that extends along the upper punch holding bore is arranged as the arrangement described in the patent document 1, a problem might occur that the powder material entering inside of the upper punch holding bore is mixed with lubricant applied to the inside of the upper punch holding bore and the mixture of the powder material and the lubricant gets stuck inside of the upper punch holding bore or the air vent groove, which increases a troublesome labor of cleaning inside of the upper punch holding bore or the air vent groove. Furthermore, if the mixture of the powder material and the lubricant gets stuck inside of the upper punch holding bore, the upper punch might be grated, which puts a heavy load on a guide rail that guides the upper punch vertically. As a result of this, problems might occur that a life of the guide rail is shortened or the guide rail is broken. In addition, a problem might occur that the powder material entering the upper punch holding bore or the air vent groove passes the upper punch holding bore and attaches to a head portion of the upper punch or the guide rail that makes an abutting contact with the head portion of the upper punch and that guides the upper punch upward slidably.
The present claimed invention intends to solve the above problems.